1. Field of the Invention
The present invention relates generally to electro magnetic status indicators, and, more particularly, to overcurrent trip indicators for a circuit interrupter of a high voltage alternating electric power system for providing indication of various overcurrent conditions occurring in the electric power system at the time the tripping operation of the circuit interrupter is initiated.
2. Prior Art
U.S. Pat. No. 4,068,283, issued Jan. 10, 1978 to Ronald R. Russell, disclosures an automatic circuit interrupter for an electric power circuit having an instantaneous trip circuit for tripping the circuit interrupter when a high fault or overcurrent flows in one or more of the phase lines, a delay trip circuit for tripping the circuit interrupter when a low or moderate fault or overcurrent flows in one or more of the phase lines, and a ground fault trip circuit for tripping the circuit interrupter upon the occurrence of a ground fault in the electric power system. Three electromagnetic overcurrent trip indicators, are actuated by the instantaneous trip circuit, the delay trip circuit, and the ground fault trip circuit, respectively. When the circuit interrupter is tripped by one of the three trip circuits, the overcurrent trip indicators associated with that one trip circuit is moved to its indicating position. Thus, after the circuit interrupter has been tripped by one of the three trip circuits, examination of the three trip indicators will disclose whether the abnormal condition of the electric power system causing the second interrupter to trip is a phase fault condition, a phase overload condition, or a ground fault condition.
However, it would be very beneficial to know, from a troubleshooting standpoint, which phase or phases of the electric power system were overloaded or faulted to initiate tripping of the circuit interrupter. Further, it would be advantageous to have trip indicators which would indicate various abnormal conditions of the electric power system at the time tripping of the circuit interrupter was initiated, even though tripping of the circuit interrupter was not a result of one of these abnormal conditions. For example, when an overload condition occurs in the electric power system, but the circuit interrupter is manually tripped before the tripping operation is initiated by an overcurrent tripping circuit, it would be desirable for the trip indicators to indicate the overload condition. Also, when the circuit interrupter automatically recloses one or more times before finally remaining open, it would be desirable to have trip indicators which were automatically reset each time the circuit interrupter was closed, so that, after a tripping operation of the circuit interrupter, the trip indicators will indicate only abnormal conditions existing in the electric power system at the time the circuit interrupter was last tripped.